Kenyan Prime minister Raila Odinga is recovering from an operation performed Tuesday to remove fluid build-up around his brain.

After initial reports that Mr. Odinga was suffering from exhaustion, doctors revealed that an operation was performed on the Kenyan prime minister to relieve pressure in his skull.

On Tuesday, Dr. Livingstone Oluoch-Olunya, who performed the surgery, said the diagnosis was made after Mr. Odinga told doctors he hit his head while entering his vehicle.

"The prime minister came into the hospital yesterday after having had a complaint of headache and a bit of fatigue," he said. "Investigations by the doctors here confirmed that he had a buildup of pressure inside his head, when he remembered having banged his head in one of his vehicles three weeks ago. The build-up of pressure required us to relieve this, which we did that last night successfully."

Doctors at Nairobi Hospital would not specify the cause of the pressure around the prime minister's brain.

According to his press secretary, Dennis Onyango, Mr. Odinga complained of headaches while visiting a clean-up project at the Nairobi Dam on Monday. He checked himself into the hospital shortly after.

The 65-year-old prime minister is one of the most prominent advocates of constitutional reform in Kenya. He has been campaigning across the country in support of a new constitution to be approved by Kenyan voters in an August referendum.

The constitutional referendum is part of a power-sharing agreement reached between Mr. Odinga and President Mwai Kibaki after a disputed presidential election in December of 2007. After accusing each other of election fraud, angry supporters across the east African nation clashed, leaving more than 1,000 dead and 300,000 displaced.

Aides to the prime minister downplayed the operation as minor, and Dr. Olunya confirmed that Mr. Odinga would be able to resume his schedule within five days.

The prime minister is expected to continue his efforts to win over opponents of the new constitution, who take issue with controversial clauses on abortion and Islamic courts.